1. Field of the Invention
The present invention relates to a seat belt winding force control device for use in a vehicle. More particularly, the present invention relates to an improvement in the retractor of a seat belt provided with a controlling member to brake the seat belt winding force.
2. Description of the Prior Art
Various types of seat belt retractors are well known in the art. Such seat belt retractors utilize an emergency brake to be operated by the wearer for retracting the seat belt.
Such seat belts are equipped to detect increasing and decreasing speed of a vehicle by measuring acceleration of the seat belt or acceleration speed of a vehicle using an electronic device. However, in such seat belt retractors, since winding force generated by a windup spring continuously exists on the seat belt while it is used, the belt wearers feel uncomfortable.
To ease the feeling of binding and to provide comfort for the belt wearer, a device designed to draw out the belt from the retractor as much as needed and fix its winding force has been proposed. Generally, such a winding force locking means performs the following functions.
The belt wearer feels that the belt is worn and then puts the locking means in operating order. However, the locking means operates before the wearer is finally seated so that the intended effect is not produced.
In order to solve such a problem, "a seat belt retractor provided with a winding force locking means," described in the U.S. Pat. No. 4,261,531 has been proposed.
The belt winding force locking means disclosed therein includes a locking means interlocked with the winding shaft means and a non-interlocked position non-interlocked with the winding shaft means. The winding force locking means when placed in the interlocked position prevents the winding of the seat belt from its wearing position. Winding of the belt in a predetermined range beyond its wearing position is drawn out. A first sensing means detects the wearing of the belt by its wearer and a second sensing means detects draw out of the belt after the belt wearer assumes a normal seated position while wearing the belt.
However, in such belt winding force locking means, in order to lock winding force, the first sensing means must function by operating a buckle which is a usual seat belt locking device and winding force must be locked by drawing out the seat belt again. In order to release the locked winding force, the buckle must be operated again. Thus, it is difficult to lock and release winding force every time while the wearer is seated. Furthermore, such locking means is complicated in construction and expensive to manufacture by comprising a first sensing means in which a ball is internally installed and a separate second sensing means, so that the seat belt directly connected with the safety of the wearer is apt to cause trouble.
Generally, the seat belt winding force control device has to meet the following requirements.
First, the seat belt is required to fulfill its function until a vehicle ceases to operate and its winding force control device has to be free from trouble nearly permanently.
Second, the winding force control device has to have a simple locking and releasing operation.
Third, the winding force control device has to have an accurate locking and releasing mechanism.
Fourth, the cost must not be increased by the addition of the winding force control means to the existing emergency braking means.
At present, however, no seat belt winding force control device which meets those requirements has been developed.